Optical receivers are an integral part of light guide systems utilized for optical communications. Optical receivers generally have a limited dynamic range which in this instance is defined as the range of optical power between the minimum allowable level for a given system margin and the maximum level before overloading occurs. Oftentimes if the transmitters and receivers are to be located at fixed distances from each other, a translucent attenuator is placed within the optical fiber at a certain point in the transmission segment such that the received signal is within the dynamic range of the receiver.
The value of the attenuator is dependent upon the distance between the transmitter and receiver. Thus, if this distance changes a different attenuator should be inserted. This becomes impractical in a subscriber loop system in that when a customer moves from one place to another, the optical receiver also has to be relocated, thereby necessitating a corresponding change in the attenuator. A need is apparent, therefore, for an optical receiver that can operate efficiently and effectively without the use of these attenuators.
Heretofore, and as is now well known in the art, a certain optical distance was considered necessary between the transmitter and receiver to prevent overloading of the receiver and thereby allow for intelligible transmission. It is now also well known in the art that the dynamic range of a typical optical receiver is around 20 dBm and that the minimum signal that the receiver can reproduce intelligibly is around 50 dBm.
Finally, as is well known, optical receivers operate within the range of -30 dBm to -50 dBm. Thus the 20 dBm of dynamic range is at the low end or when the optical receiver and transmitter are the farthest distance apart from each other. And when the receiver and transmitter are at the "high" end or close together, overloading of the receiver generally occurs.
Heretofore, there have been attempts to improve the dynamic range of optical receivers. Oftentimes these attempts have required complex circuitry for implementation. Thus, there is a corresponding increase in cost associated with such circuitry which reduces the cost effectiveness of the solution.